1. Field of the Invention
The invention relates generally to columns and methods for producing microcolumns suitable for use in gas chromatographs. In particular, following deposition of the stationary phase coating, the microcolumns are subjected to a postcoating treatment with a molecule that binds to the active sites in the stationary phase column thereby reducing or eliminating loss of gas chromatograph performance associated with those active sites.
2. Related Art
A gas chromatograph (GC) is a chemical analysis instrument used for separating chemicals in a complex sample and is generally composed of three basic parts, an injector, a column, and a detector. Different chemical constituents of a sample pass in a gas stream through the column at different rates depending on their various chemical and physical properties and their interaction with a specific column filling, called the stationary phase. As the chemicals exit the end of the column, they are detected and identified electronically. Conventional GC columns are generally small open tubes with internal diameters in the range of about 270 microns to about 530 microns and lengths in the range of about 10 meters to 30 meters. The inside walls of these columns are coated with a thin even layer of organic polymer, the GC liquid phase, to a thickness of less than about one micron.
Microfabricated gas chromatograph (μGC) column development has received considerable interest for the analysis of toxic chemicals, explosives, disease markers and other analytes. In general, column fabrication starts with first etching microfluidic channels in a silicon or glass wafer and then sealing the etched microfluidic channels using anodic or fusion bonding. The microcolumn walls are then deactivated. Subsequently, static or dynamic coating techniques may be used to deposit the stationary phase inside the microcolumn prior to analyte analysis.
Many studies have reported columns that can separate hydrocarbons and a few studies have reported microfabricated columns that are able to show significant separation of organophosphonates. In the organophosphonate separation studies, however, the organophosphonate peaks exhibit significant tailing due to unwanted adsorption to the active sites present in the microcolumn. FIG. 1 shows a fast μGC chromatogram, however, most noteworthy is that the dimethyl methyl phosphonate (DMMP), diethyl methyl phosphonate (DEMP), and diisopropyl methyl phosphonate (DIMP) peaks tail, which makes the microcolumns less than optimal for fast portable GC. Accordingly, there is a need for improved deactivation of the walls of columns, particularly in microcolumns suitable for use in GCs and μGCs.